Atypical Cervical Vertebrae: C1/Atlas

Question 1

What is the name of the first cervical vertebra?

Answer 1

Atlas

Question 2

What features are lacking at C1?

Answer 2

• Vertebral body
• pedicles
• a spinous process
• intervertebral disc

Question 3

What is thought to represent the pedicle at C1?

Answer 3

The anterior arch

Question 4

What osseous modification is observed to the front of the anterior arch of C1?

Answer 4

The anterior tubercle

Question 5

What muscle attaches to the anterior arch of C1?

Answer 5

Longus colli

Question 6

What ligaments will attach to the anterior arch of C1?

Answer 6

• anterior longitudinal
• anterior Atlanta-occipital
• anterior atlanto-axial

Question 7

What is observed on the back of the anterior arch of C1?

Answer 7

the fovea dentis

Question 8

What joint classifications are observed on the anterior arch of C1?

Answer 8

fibrous (amphiarthrosis) syndesmosis joint and synovial pivot (diarthrosis trochoid) joint

Question 9

What is the contribution of the lateral mass to the circumference of C1?

Answer 9

forty percent - twenty percent for each lateral mass

Question 10

What is the morphology of the superior articular facet of C1?

Answer 10

they are elliptical, closer together in front and often demonstrate an elevation subdividing the facet surface into two separate surfaces

Question 11

What is the orientation of the superior articular facet of C1?

Answer 11

backward, upward, medial (BUM)

Question 12

What is the joint classification of the atlanto-occipital zygapophysis?

Answer 12

synovial (diarthrosis) ellipsoidal joint

Question 13

What are the morphological characteristics of the inferior articular facet of C1?

Answer 13

asymmetrical, slightly concave or flattened

Question 14

What is the orientation of the inferior articular facet of C1?

Answer 14

backward, medial, downward (BMD)

Question 15

What is the joint classification of the atlanto-axial zygapophysis?

Answer 15

synovial plane (diarthrosis arthrodia) joint

Question 16

What is the name of the rounded elevation on the medial aspect of the lateral mass of C1?

Answer 16

tubercle for the transverse atlantal ligament

Question 17

What muscles attach to the lateral mass of C1?

Answer 17

• levator scapula
• splenius cervicis
• rectus capitis anterior

Question 18

What is the contribution of the posterior arch to the circumference of C1?

Answer 18

about forty percent

Question 19

What part of C1 represents the spinous process?

Answer 19

posterior tubercle of the posterior arch

Question 20

What is the distance from the posterior tubercle of the posterior arch to the skin in each gender?

Answer 20

• male: about fifty millimeters

- female: about thirty-seven millimeters

Question 21

What attaches to the posterior tubercle of the posterior arch of C1?

Answer 21

• rectus capitis posterior minor

- ligamentum nuchae

Question 22

What superior surface modifications of the posterior arch of C1 are present?

Answer 22

• groove/sulcus for the vertebral artery

- arcuate rim

Question 23

What attaches to the arcuate rim of C1?

Answer 23

the posterior atlanto-occipital ligament

Question 24

What are the attachment sites of the posterior atlanto-occipital ligament?

Answer 24

• arcuate rim of the posterior arch of atlas
• superior articular process of the lateral mass of atlas
• posterior margin of the foramen magnum of the occipital bone

Question 25

Ossification of the free margin of the posterior atlanto-occipital ligament results in which atypical bone classification?

Answer 25

accessory bone

Question 26

What is the earliest age of development where ossification of the anterior free margin of the posterior atlanto-occipital ligament was observed?

Answer 26

about age 7 years old

Question 27

Based on the amount of ossification of the anterior free margin of the posterior atlanto-occipital ligament what structures will form?

Answer 27

an incomplete ponticulus posticus or a complete ponticulus posticus

Question 28

What are the attachment sites of the ponticulus posticus?

Answer 28

- arcuate rim of the posterior arch of atlas | - superior articular process of the lateral mass of atlas

Question 29

What other name may be used to identify a ponticulus posticus?

Answer 29

Kimmerle's anomaly

Question 30

What names are given to the opening formed by the ponticulus posticus?

Answer 30

arcuate foramen or retroarticular canal

Question 31

Ponticulus posticus has been observed in what ethnic populations?

Answer 31

all ethnic populations studied thus far

Question 32

What is the general range of incidence of ponticulus posticus in the populations studied?

Answer 32

1% - 4%

Question 33

What is the gender bias now associated with ponticulus posticus?

Answer 33

female

Question 34

What is the incidence of a complete ponticulus posticus versus an incomplete ponticulus posticus?

Answer 34

- the incidence of a complete ponticulus posticus is about 15% - the incidence of an incomplete ponticulus posticus may be as high as 41%

Question 35

What is observed on the undersurface of the posterior arch of C1?

Answer 35

- inferior vertebral notch | - an attachment site for the posterior atlanto-axial ligament

Question 36

What joint classification(s) may be observed on the posterior arch of C1?

Answer 36

fibrous (amphiarthrosis) syndesmosis joint

Question 37

What is the location of the zygapophysis relative to the atlanto-occipital and atlanto-axial intervertebral foramina?

Answer 37

if forms part of the anterior boundary of the intervertebral foramen in both cases

Question 38

What is the general appearance of the transverse process of C1?

Answer 38

triangular

Question 39

What are the osseous parts of the transverse process of C1?

Answer 39

- costal element - posterior tubercle - true transverse process

Question 40

What osseous parts of the transverse tubercle are absent at C1?

Answer 40

- anterior tubercle | - costotransverse bar

Question 41

What muscles attach to the transverse process of C1?

Answer 41

- rectus capitis anterior - rectus capitis lateralis - middle scalene - levator scapula - splenius cervicis - obliquus capitis superior - obliquus capitis inferior - intertransversarii

Question 42

What suboccipital muscles are known to have fascial projections attaching to the spinal dura?

Answer 42

- rectus capitis posterior major - rectus capitis posterior minor - obliquus capitis inferior

Question 43

What are the connections between suboccipital muscles and the spinal dura called?

Answer 43

myodural bridges

Question 44

What are the lateral bridges of atlas connected to?

Answer 44

lateral mass and transverse process of atlas

Question 45

What forms of the lateral bridges are observed in the population?

Answer 45

incomplete lateral bridges and complete lateral bridges

Question 46

What opening is identified when a complete lateral bridge is formed?

Answer 46

the retrotransverse foramen

Question 47

What are the possible contents of the retrotransverse foramen?

Answer 47

- vertebral artery - branch from the suboccipital nerve - veins communicating with the venous sinuses of the neck

Question 48

Which of the ponticles (bridges) of atlas is most numerous?

Answer 48

ponticulus posticus

Question 49

Which of the ponticles (bridges) of atlas is only observed in humans?

Answer 49

lateral bridges

Question 50

What is observed in the transverse foramen of C1?

Answer 50

- vertebral artery - vertebral venous plexus - postganglionic sympathetic motor nerve fibers

Question 51

What is the gender variation for measurements of the transverse diameter of C1?

Answer 51

- males: 78 millimeters | - females: 72 millimeters

Question 52

Is there a gender difference for the distance from the posterior tubercle of the transverse process of C1 to the skin?

Answer 52

not a significant difference

Question 53

What is the distance from the posterior tubercle of the transverse process of C1 to the skin for each gender?

Answer 53

a little over 30 millimeters for both male and female

Question 54

What joint classifications are observed at C1?

Answer 54

- fibrous (amphiarthrosis) syndesmosis joint - synovial (diarthrosis) ellipsoidal joint - synovial pivot (diarthrosis trochoid) joint - synovial plane (diarthrosis arthrodia) joint

Question 55

How many synovial joint surfaces are observed at C1?

Answer 55

five

Question 56

What synovial joint surfaces are observed at C1?

Answer 56

- two superior articular facets - two inferior articular facets - fovea dentis